Charged particle radiation device with bandpass detection

ABSTRACT

Disclosed is a charged particle radiation device having a charged particle source which generates a charged particle as a probe, a charged particle optical system, a sample stage, a vacuum discharge system, an aperture which restricts a probe, a conductive film, and a charged particle detector, wherein the conductive film is provided at a position excluding the optical axis of the optical system between the sample stage and the aperture; and the distance between the sensing surface of the surface of the charged particle detector and the sample stage is larger than the distance between the sample stage and the conductive film, so that the surface of the conductive film and the sensing surface of the detector are inclined.

TECHNICAL FIELD

The present invention relates to a charged particle radiation device,particularly to a technology in which, in a charged particle radiationdevice for obtaining information of a surface of a sample by detecting asecondary particle generated from the sample with an electron beamtypically accelerated at an accelerating voltage of 1 kV through 200 kVas a probe, with regard to an energy of an electron to be detected, theenergy is detected by subjecting the energy to band-pass discriminationeffectively and simply.

BACKGROUND ART

In a charged particle beam device which irradiates a top of a samplewith a charged particle as a probe, detects a secondary particle that isgenerated from the sample in accordance with the irradiation, or acharged particle that transmits through the sample, and obtainsinformation with regard to a probe irradiation position from anintensity that is detected, there are presented a number of methods ofobtaining specific information by selecting and detecting an energy ofthe charged particle.

Particularly, in a scanning electron microscope which obtains atwo-dimensional image of a scanning region by two-dimensionally scanningan electron beam probe on a sample, there are presented a number ofmethods of discriminating to detect an energy of a signal electron thatis generated from the sample.

As methods of using the fact that a signal electron draws a trajectorywhich differs by an energy, there are presented methods of JapaneseUnexamined Patent Application Publication No. 2004-221089 (applicant:Leo Elektronenmikroskopie GmbH), and Japanese Unexamined PatentApplication Publication No. 2002-110079 (applicant: Hitachi, Ltd.) whichprovide a sensing surface of a detector at a position at which only anelectron of a specific energy is detected.

As methods of using a porous plate-like electrode (mesh electrode) whichapplies a negative voltage that supplies an electric field of shieldingan electron of a specific energy or less at an interval between a sampleand a sensing surface of a detector in a case where a trajectory of asignal electron is not changed by an energy, there are presented methodsof Japanese Unexamined Patent Application Publication No. Hei11(1999)-242941 (applicant: Hitachi, Ltd.), and WO Publication No.99/46798 (applicant: Hitachi, Ltd.).

However, all of these methods are methods for carrying out high-passdetection, or low-pass detection. It has been impossible, for example,to carry out band-pass detection which emphasizes to detect only anelectron of 10 keV through 20 keV in a signal electron which has anenergy width of 1 keV through 30 keV when an irradiation energy of aprimary electron beam is 30 keV.

As methods of carrying out band-pass detection, there are presentedvarious kinds of methods of making multi-stage electric field barriersbetween plural mesh electrodes by applying voltages which differ insteps on the plural electrodes, and confining signal electrons energyband-passes of which are selected into respective potential barriers anddetecting the signal electrons.

In Japanese Unexamined Patent Application Publication Hei10(1998)-188883 (applicant: SHIMADZU CORPORATION), there is presented amethod of detecting signal electrons band-passes of which are selectedas current signals from respective mesh electrodes via floatingamplifiers. In Japanese Unexamined Patent Application Publication No.2006-114426 (applicant: Hitachi, Ltd.), there is presented a method ofdetecting a signal electron a band-pass of which is selected by anelectron detector which is provided at an interval of mesh electrodes.

However, according to the methods, there pose problems by nonuniformityof an electric field by using the mesh electrode and a three-dimensionalobstacle by the electrode, and effective detection cannot be expected.Furthermore, both of the methods need plural high voltage power sourcesfor supplying the shielding electric fields, and it is necessary tocontrive to provide a pertinent electrostatic withstand voltage.Therefore, a simple and convenient detector is not configured.

In Japanese Unexamined Patent Application Publication No. Hei11(1999)-160438 (applicant: EL-MUL TECHNOLOGIES LTD.), there ispresented a method of providing a thin film between a sensing surface ofan MCP (microchannel plate) detector which is an electron detector and asample. An object thereof resides in an effective detection of a highenergy electron even in an MCP sensitivity of which is maximized at alow energy of about 300 eV. The high energy electron is subjected to anenergy attenuation by the thin film and transmits through the thin filmfrom a side of the sensing surface of the MCP. Or, the high energyelectron is transformed into a subsidiary electron of an extremely lowenergy (<100 eV) on the side of the sensing surface of the MCP of thethin film. Thereby, the high energy electron can effectively be detectedby MCP by detecting the extremely low energy electron after thetransformation at high sensitivity.

According to the method, it is anticipated that band-pass detection canbe carried out when a film thickness of the thin film is pertinentlyselected, and an electron of a desired energy is transformed to have anenergy of precisely about 300 eV. However, the more hardly the energy isattenuated, the more the extremely low energy electron that is producedby the high energy electron on the surface of MCP is detected. As aresult, only an effect as a high-pass filter is expected. It isanticipated that it is impossible to carry out band-pass detection whichis achieved by not detecting the high energy electron.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2004-221089

Patent Literature 2: Japanese Unexamined Patent Application PublicationNo. 2002-110079

Patent Literature 3: Japanese Unexamined Patent Application PublicationNo. Hei 11(1999)-242941

Patent Literature 4: WO Publication No. 99/46798

Patent Literature 5: Japanese Unexamined Patent Application PublicationNo. Hei 10(1998)-188883

Patent Literature 6: Japanese Unexamined Patent Application PublicationNo. 2006-114426

Patent Literature 7: Japanese Unexamined Patent Application PublicationNo. Hei 11(1999)-160438

SUMMARY OF INVENTION Technical Problem

As described above, simple and highly efficient band-pass detection ofan electron has been difficult in any of technologies disclosed in thecited Patent Literatures 1 through 7 shown above.

It is an object of the present invention to provide an image of ascanning electron microscope having a simple and efficient energyband-pass of an electron with regard to an electron an energy of whichis equal to or higher than 1 kV and equal to or lower than anirradiation energy of a primary electron beam which is generated from asample in a scanning electron microscope that uses a primary electronbeam accelerated typically at 1 kV through 200 kV as a probe.

Solution to Problem

According to the present invention, the problem described above isachieved by a combination of a conductive film which is provided at aninterval between an aperture that restricts a probe irradiated to asample and a sample stage, and an electron detector which has a sensingsurface that has an angle of 30° through 150° relative to the conductivefilm, in a charged particle radiation device.

Advantageous Effects of Invention

According to such a configuration, simple and highly efficient band-passdetection can be carried out by a minimum configuration which does notneed a high voltage and which does not have a three-dimensional obstaclesuch as a mesh.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1-1 is a diagram showing a basic configuration of a band-passdetector according to the present invention.

FIG. 1-2 is a diagram showing a basic configuration of a band-passdetector according to the present invention.

FIG. 1-3 is a diagram showing a basic configuration of a band-passdetector according to the present invention.

FIG. 1-4 is a diagram showing a basic configuration of a band-passdetector according to the present invention.

FIG. 2 is a diagram showing a scanning electron microscope according toa first embodiment.

FIG. 3 is a diagram showing a scanning electron microscope according toa second embodiment.

FIG. 4 is a diagram showing a scanning electron microscope according toa third embodiment.

FIG. 5 is a diagram showing a scanning electron microscope according toa fourth embodiment.

FIG. 6 is a diagram showing a scanning electron microscope according toa fifth embodiment.

FIG. 7 is a diagram showing a scanning electron microscope according toa sixth embodiment.

FIG. 8 is a diagram showing a scanning electron microscope according toa seventh embodiment.

FIG. 9 is a diagram showing a scanning electron microscope according toan eighth embodiment.

FIG. 10 is a diagram showing a scanning electron microscope according toa ninth embodiment.

FIG. 11 is a diagram showing a scanning electron microscope according toa tenth embodiment.

FIG. 12 is a diagram showing a scanning electron microscope according toan eleventh embodiment.

FIG. 13 is a diagram showing a scanning electron microscope according toa twelfth embodiment.

FIG. 14 is a diagram showing scanning electron microscope according to athirteenth embodiment.

FIG. 15 is a diagram showing a mechanism of making a band-pass detectionenergy variable in a band-pass detector according to the presentinvention.

FIG. 16 is a diagram showing a second mechanism for making a band-passdetection energy variable in a band-pass detector according to thepresent invention.

FIG. 17 is a diagram showing a low vacuum scanning electron microscopeaccording to a fourteenth embodiment.

FIG. 18 is a diagram showing a low vacuum scanning electron microscopeaccording to a fifteenth embodiment.

FIG. 19 is a diagram showing a low vacuum scanning electron microscopeaccording to a sixteenth embodiment.

DESCRIPTION OF EMBODIMENTS

FIG. 1-1 shows a configuration which becomes a basis of an energyband-pass electron detector according to the present invention.

Hereinafter, for convenience of an explanation, of electrons having anenergy equal to or higher than 1 keV and equal to or lower than anirradiation energy of a primary electron beam, an electron having anenergy higher than a desired energy which is intended to be subjected toband-pass detection is referred to as a high energy electron, and anelectron having an energy lower than the desired energy is referred toas a low energy electron. Also, an electron having an energy equal to orlower than 100 eV is referred to as an extremely low energy electron.

A conductive film 1 of aluminum, gold or the like having a thickness of10-50000 nm is arranged on trajectories of signal electrons 5, 4, and 7.At this time, the conductive film 1 is arranged vertically to a primaryelectron beam with a likelihood of ±10°. An electron detector 2 in whicha sensing surface thereof has an angle of 30° through 150° (90° in FIG.1-1) relative to the conductive film 1 is arranged at a position whichis remote from a sample by more than a distance between the conductivefilm 1 and the sample. At this time, the conductive film 1 is arrangedto stay away from an optical axis of the primary electron beam 3 forpassing the primary electron beam 3.

In signal electrons which are generated from the sample, the low energyelectron 4 uses all the energy during a procedure of advancing in theconductive film, and is stopped at a position near to a face of theconductive film 1 on a side of the sample. Therefore, in the electrondetector 2, a signal caused by the low energy electron is not detected.

The desired energy electron 5 advances although an energy thereof isbeing lost in the conductive film and transmits through the conductivefilm from a face of the conductive film on a side of the detector with alow energy equal to or lower than 1 keV. At this time, the electron 6 ofan extremely low energy (several eV) is generated from a face of theconductive film on a side of the detector. As is generally known, a rateof generating the extremely low energy electron which is generated inimpacting the electron depends on an energy of the electron impacted anda material of a substance impacted, and in a number of substances, therate has a maximum value when the energy of the electron impacted isequal to or lower than 1 keV. It is known that in aluminum, the rate ofgenerating the extremely low energy electron 6 is maximized by theelectron of about 500 eV and is about 2.

On the other hand, the high energy electron 7 hardly loses the energy inthe conductive film and passes through the conductive film by atrajectory which is substantially near to a linear line. The energy inpassing through the conductive film is high, and therefore, theextremely low energy electrons which are generated from the face of theconductive film on the side of the detector are reduced. It is knownthat in aluminum, the rate of generating the extremely low energyelectron 6 by the electron of about 10 keV is about 0.2.

As described above, by detecting the extremely low energy electron 6,only a signal which is caused by the electron of the desired energy canselectively be detected with emphasis, and band-pass detection of theelectron is realized. When the signal obtained here is displayed at animage processing terminal in synchronism with scanning of the primaryelectron beam 3, there can be provided an image of the scanning electronmicroscope by the electron which is subjected to band-pass by thedesired energy.

The electron detector 2 of detecting the extremely low energy electron 6includes a scintillator 9, a photomultiplier 11, and a light guide 10 ofguiding a photon which is generated from the scintillator to thephotomultiplier. According to the embodiment shown here, a face of thescintillator which is a sensing surface of the detector is arranged withan angle of 90° relative to the conductive film. The angle of thesensing surface of the detector and the conductive film is not limitedto 90° but the face of the scintillator may be arranged by an anglewithin a range equal to or larger than 30° and equal to or smaller than150°. A surface of the scintillator 9 of the electron detector isprovided with an accelerating electrode 12 in a shape of a thin film ofapplying a positive voltage of about 10 kV for accelerating the secondelectron. The accelerated extremely low energy electron 6 is impacted tothe scintillator 9, and generates a photon. The photomultiplier 11converts the photon into an electron to thereafter amplify with a highgain. Incidentally, the electron detector 2 is not limited to theconfiguration described above but may be, for example, an MCP(microchannel plate).

In order to prevent the high voltage which is applied to theaccelerating electrode 12 from effecting influence on the primaryelectron beam 3, there may be provided an electrode 8 in a mesh-likeshape which is maintained at the ground potential between theaccelerating electrode 12 and an optical axis of the primary electronbeam 3. A hole diameter of the mesh electrode 8 needs to be small to adegree by which an electric field produced by the accelerating electrode12 does not effect an influence on the primary electron beam 3. However,the hole diameter needs to be large to a degree by which the electricfield permeates the conductive film 1 which is a portion of generatingthe extremely low energy electron 6 to a degree of drawing the extremelylow energy electron 6 to the scintillator 9.

In order to select an energy band subject to band-pass detection, athickness of the conductive film 1 may be changed. For example, in acase where the conductive film is made of aluminum, a hole diameter maybe made to be about 1 μm in a case where there is carried out band-passdetection in which the energy centers on 10 keV, and may be about 2.5 μmin a case where there is carried out band-pass detection in which theenergy centers on 20 keV. In a case where band-pass detection is carriedout in which the energy centers on a lower energy, the thickness of theconductive film may further be thinned.

In a case where the present detector is intended to be used as ahigh-pass filter, the thickness of the conductive film 1 may be selectedsuch that an energy of a signal electron having a maximum energy (avalue of which is substantially the same as that of the irradiationenergy of the primary electron beam) is attenuated to a low energy equalto or lower than 1 keV.

The face of the conductive film on the side of the detector may becoated with a substance such as MgO, Csl, an aluminum oxide or the likehaving a thickness equal to or smaller than 100 nm in order to increaseefficiency of generating the extremely low energy electron.

The electron detector 2 of detecting the extremely low energy electron 6includes the scintillator 9, the photomultiplier 11, and the light guide10 of guiding the photon that is generated from the scintillator to thephotomultiplier.

The high energy electron 7 needs to be prevented from being detecteddirectly as a condition which is indispensable for using theconfiguration of the detector as the band-pass filter. This is achievedby contriving an arrangement of the conductive film 1 and a face of thescintillator 9 which is the sensing surface of the detector.

According to the embodiment shown in FIG. 1-1, the conductive film isarranged vertically to the optical axis of the primary electron beam 3,and the face of the scintillator 9 which is the sensing surface of thedetector is arranged relative to the conductive film with the angle of90°. Here, attention should be paid so that the high energy electron 7in which a change 101 in an angle of a trajectory of the electron 7 inpassing the conductive film is confined to a change of ±10° or less isprevented from entering the sensing surface directly. Such anarrangement of the conductive film 1 and the sensing surface needs to bemade for all of the embodiments hereinbelow.

The angle between the conductive film and the optical axis of theprimary electron beam 3 and the angle between the sensing surface of thedetector and the conductive film are not limited to 90°. An explanationwill be given as follows of a variation in the angle between theconductive film and the sensing surface of the detector in the basicconfiguration of FIG. 1-1.

The angle between the conductive film and the optical axis of theprimary electron beam is not limited to 90°±10° but may be an angle of,for example, 100° through 150°. At this time, the angle between theconductive film and the sensing surface of the detector is made to fallwithin a range of 30° through 150°. In an embodiment shown in FIG. 1-2,the conductive film 1 and the optical axis of the primary electron beam3 are arranged with an angle of 120° therebetween. Also, the conductivefilm 1 and the face of the scintillator 9 which is the sensing surfaceof the detector are arranged with an angle of 60° therebetween.According to such a configuration, a direction of an initial speed of anumber of the extremely low energy electrons 6 is directed to adirection of the sensing surface and detection efficiency is increased.

According to an embodiment shown in FIG. 1-3, the conductive film 1 andthe optical axis of the primary electron beam 3 are arranged with theangle of 120° therebetween. Also, the conductive film 1 and the face ofthe scintillator which is the sensing surface of the detector arearranged with an angle of 90° therebetween. According to such aconfiguration, the direction of the initial speed of a number of theextremely low energy electrons 6 is directed in the direction of thesensing surface and the detection efficiency is increased. In additionthereto, the high energy electron 7 which transmits through theconductive film 1 is made to be difficult to directly enter the surfaceof the scintillator 9 which is the sensing surface.

According to an embodiment shown in FIG. 1-4, the conductive film 1 andthe optical axis of the primary electron beam 3 are arranged with theangle of 90° therebetween. Also, the conductive film 1 and the face ofthe scintillator 9 which is the sensing surface of the detector arearranged with an angle of 120° therebetween. According to such aconfiguration, the high energy electron 7 which transmits through theconductive film 1 is made to be difficult to enter directly to the faceof the scintillator 9 which is the sensing surface.

An explanation will be given as follows of representative embodiments ofthe present invention in reference to the drawings.

First Embodiment

FIG. 2 shows a first embodiment of the present invention and is a viewshowing a total configuration of a scanning electron microscopeincluding an energy band-pass electron detector.

The scanning electron microscope shown in FIG. 2 is generally configuredby an electro-optical lens-barrel 13 including a mechanism ofirradiating a sample with an electron beam, a sample base 49 which holdsa sample 50, and a sample chamber 14 which stores the sample base 49, aninformation processing unit (not illustrated) which carries out controlprocessing, various image processing, or information processing (notillustrated) which is related to a user interface as well as an imagedisplay terminal (not illustrated) which displays a scanning electronmicroscope image, and an image memory.

The electro-optical lens-barrel 13 is basically configured by anelectron source 15, a first condenser lens (C1 lens) 16, a secondcondenser lens (C2 lens) 17, two stages of scanning deflectors 18, anobject lens 21 and the like. As the electron source 15, an electronsource of an electric field emitting type is typically used.

The object lens 21 is an object lens of a semi-in-lens type ofintentionally permeating in an output magnetic field toward the sample50 which is arranged downward from a lower face of the lens. There isalso a case where the object lens 21 is arranged at an inner portion ofthe sample chamber 14 in view of a position thereof. However, forconvenience of explanation, an explanation will be given such that theobject lens 21 is a configuration element which belongs to theelectro-optical lens-system barrel 13.

The primary electron beam 3 having an energy equal to or smaller than200 keV which is emitted from the electron source 15 is converged to afirst convergent point 23 by the C1 lens 16, and later passes through anaperture 24. At this time, an unnecessary region of the primary electronbeam 3 is removed. A position of the first convergent point 23 of theprimary electron beam 3 is controlled by controlling the C1 lens 16.

The primary electron beam 3 which passes through the aperture 24 isconverged to a second convergent point 25 by the C2 lens 17. A positionof the second convergent point 25 of the primary electron beam 3 iscontrolled by controlling the C2 lens 17. The primary electron beam 3which passes through the second convergent point 25 is converged ontothe sample 50 by the object lens 21. The two stages of scanningdeflectors 18 are arranged between the C2 lens 17 and the object lens21, and the convergent point on the sample 50 of the primary electronbeam 3 is two-dimensionally scanned in accordance with a desired rangeof field of view/magnification.

Signal electrons of various energies are generated from the sample by anirradiation of the primary electron beam 3. Here, for convenience ofexplanation, in a case where the sample is at the ground potential,among signal electrons emitted from the sample, a signal electron havingan energy equal to or smaller than about 50 eV is particularly referredto as a secondary electron 26. The secondary electron, influenced by amagnetic field produced by the semi-in-lens, passes through a centerhole of the object lens 21 by being wound around the optical axis of theprimary electron beam and advances in a direction of the electronsource. At E×B20 for detector A, the secondary electron 26 is deflectedin a direction of a detector A19. The secondary electron 26 is detectedby the detector A19. The detector A19 is the same as the electrondetector 2 shown in FIG. 1-1. Notation E×B designates an orthogonalelectromagnetic field generator that linearly advances the primaryelectron beam and deflects only an electron of an extremely low energy(<50 eV) to out of axis.

In a band-pass detector, among signal electrons having an energy rangeof from 1 keV to an irradiation voltage of the primary electron beam, asignal electron having an energy in correspondence with a thickness of aconductive film is detected with emphasis. Similarly to the secondaryelectron, also the signal electron having the energy range of from 1 keVto the irradiation energy of the primary electron beam is influenced bythe magnetic field produced by the semi-in-lens, and a number of thesignal electrons pass through the center holes of the object lens 21 bybeing wound around the optical axis of the primary electron beam andadvance in the direction of the electron source.

A conductive film A43 for band-pass detection is configured by anaxisymmetric circular disk shape which is provided with a hole forpassing the primary electron beam 3 at a center thereof, and is arrangedvertically to the optical axis of the primary electron beam 3 at aninterval between E×B20 for the detector A and the C2 lens 17. At thistime, a thickness of the conductive film A43 is previously determined byan energy which is intended to be subjected to band-pass detection. Theextremely low energy electron 6 which is generated by the desired energyelectron 5 is detected by a detector B27. The detector B27 is configuredsimilarly to the electron detector 2 shown in FIG. 1-1. E×B30 for adetector B which operates similarly to E×B20 for the detector A may beprovided at an interval between the conductive film A43 and the C2 lens17.

At the detector A19, also an extremely low energy electron 29 which isgenerated by the low energy electron 4 at the face of the conductivefilm A43 on the side of the sample can also be detected in addition tothe secondary electron 26. In a case where information of the secondaryelectron 26 is intended to cut by particularly emphasizing onlyinformation of the low energy electron, a negative voltage is applied toa shielding electrode 28. The voltage at this time is typically about−100 V. In this case, the secondary electron 26 is pushed back in thedirection of the sample by a shielding electric field, and therefore,the low energy electron can be detected by the detector A19.

Second Embodiment

FIG. 3 shows a second embodiment of the present invention, and is adiagram showing a total configuration of a scanning electron microscopeincluding an energy band-pass electron detector. According to thepresent embodiment, the conductive film A43 that is configured in theaxisymmetric circular disk shape provided with the hole of passing theprimary electron beam 3 at the center is arranged by an angle equal toor smaller than 150° relative to the optical axis of the primaryelectron beam 3. According to the method, the extremely low energyelectron 6 has an initial speed in a direction of the detector B27, andtherefore, the detection is made to be easy without using E×B30 for thedetector B explained in the first embodiment. Similarly, when thedetector A19 is arranged as shown in FIG. 3, since the extremely lowenergy electron 29 has an initial speed in the direction of the detectorA, and therefore, the detection is made to be easy without using E×B20for the detector A.

Third Embodiment

FIG. 4 shows a third embodiment of the present invention and is adiagram showing a total configuration of a scanning electron microscopeincluding an energy band-pass electron detector. According to thepresent embodiment, particularly in order to detect an electron which isemitted from the sample at a large angle (high angle) (high angleelectron), in addition to the first embodiment, one more system of aband-pass detecting system is provided. A conductive film B31 forband-pass detection of the high angle electron is configured by anaxisymmetric circular disk shape provided with a hole of passing theprimary electron beam 3 at a center thereof, and is arranged verticallyto the optical axis of the primary electron beam 3 at an intervalbetween the aperture 24 and the C2 lens 17. At this time, a thickness ofthe conductive film B31 is determined by an energy which is intended tosubject to band-pass detection. The extremely low energy electron 33which is generated by the high angle electron 32 of a desired energy isdetected by a detector C34. The detector C34 is configured similarly tothe electron detector 2 shown in FIG. 1-1. E×B35 for the detector Cwhich operates similarly to E×B20 for the detector A may be provided atan interval between the conductive film B31 and the aperture 24.

Incidentally, according to the third embodiment, the detector B24 andE×B30 for the detector B are not necessarily needed. In that case, onthe side of the sample of the C2 lens 17, band-pass detection is notcarried out, and it is not necessary that the thickness of theconductive film A43 is equal to or less than 50000 nm. Also, theconfiguration of the side of the sample of the C2 lens 17 may be similarto that in the second embodiment.

Fourth Embodiment

FIG. 5 is a diagram showing a fourth embodiment of the present inventionand a total configuration of a scanning electron microscope including anenergy band-pass electron detector. According to the present embodiment,the conductive film B31 is inclined similarly to the conductive film A43of the second embodiment. Similarly to the second embodiment, there isprovided a detector D38 in order to detect the extremely low energyelectron 37 that is generated by a high angle electron 36 of a lowenergy at a face of the conductive film B31 on the side of the sample.

Incidentally, according to the fourth embodiment, the detector B27 andE×B30 for the detector Bare not necessarily needed. In that case,band-pass detection is not carried out under the C2 lens 17, and it isnot necessary that the conductive film A43 has a thickness equal to orless than 50000 nm.

Also, a configuration on the sample side of the C2 lens 17 may besimilar to that of the second embodiment.

Fifth Embodiment

FIG. 6 is a diagram showing a fifth embodiment of the present inventionand a total configuration of a scanning electron microscope including anenergy band-pass electron detector. According to the present embodiment,there is provided one more system of a band-pass detection system inaddition to the first embodiment in order to further subject the highenergy electron 7 to band-pass detection. A conductive film C39 forband-pass detection is configured in an axisymmetric circular disk shapeprovided with a hole of passing the primary electron beam 3 at a centerthereof and is arranged vertically to the optical axis of the primaryelectron beam 3 at an interval between the conductive film A43 and theC2 lens 17. At this time, a thickness of the conductive film C39 isdetermined by an energy of an electron which is intended to be subjectedto band-pass detection. An extremely low energy electron 40 which isgenerated by the high energy electron 7 of a desired energy is detectedby a detector E41. The detector E41 is configured similarly to theelectron detector 2 shown in FIG. 1-1. E×B42 for the detector E whichoperates similarly to E×B20 for the detector A may be provided at aninterval between the conductive film C39 and the aperture 24.

Sixth Embodiment

FIG. 7 is a diagram showing a sixth embodiment of the present inventionand a total configuration of a scanning electron microscope including anenergy band-pass electron detector. According to the present embodiment,there is provided one more system of a band-pass detecting system inaddition to the second embodiment in order to detect the high energyelectron 7. A conductive film C39 for band-pass detection is configuredby an axisymmetric circular disk shape provided with a hole of passingthe primary electron beam 3 at a center thereof and is arranged at aninterval between the conductive film A43 and the C2 lens 17 in a stateof being inclined to the optical axis of the primary electron beam 3 byan angle equal to or smaller than 150°. At this time, a thickness of theconductive film C39 is determined by an energy of an electron which isintended to be subjected to band-pass detection. An extremely low energyelectron 40 which is generated by the high energy electron 7 of adesired energy is detected by a detector E41. The detector E41 isconfigured similarly to the electron detector 2 shown in FIG. 1-1.

Configurations 39, 40, 41, and 42 configuring the detecting system fordetecting the high energy electron explained in the fifth embodiment maybe arranged at an interval between the conductive film B31 (E×B35 forthe detector C in a case of providing E×B35 for the detector C) of thethird embodiment shown in FIG. 4 and the aperture 24. In that case, thehigh energy electron of the high angle which passes through theconductive film B31 can be detected.

Also, the configurations 39, 40, and 41 configuring the detecting systemfor detecting the high energy electron explained in the sixth embodimentmay be arranged at an interval between the conductive film B31 of thefourth embodiment shown in FIG. 5 and the aperture 24. In that case, thehigh energy electron of the high angle which passes through theconductive film B31 can be detected.

Seventh Embodiment

FIG. 8 is a diagram showing a seventh embodiment of the presentinvention and a total configuration of a scanning electron microscopeincluding an energy band-pass electron detector.

In the scanning electron microscope shown in FIG. 8, in comparison withthe first embodiment shown in FIG. 2, positions of the aperture 24 andthe C12 lens 17 are exchanged. This is an electro-optical lens-barrelwhich is effective in a case of using an electron source such as atungsten thermoelectron gun having a large light source diameter while aradiation angle current density is large, and the C1 lens 16 and the C2lens 17 are used for reducing the primary electron beam 3. The otherconfiguration is similar to that of the first embodiment, and the energyband-pass detection is carried out similarly to the first embodiment. Inthis case, the conductive film A43 is arranged vertically to the opticalaxis of the primary electron beam 3 at an interval between E×B20 for thedetector A and the aperture 24. Incidentally, similarly also in thescanning electron microscopes from the second embodiment to the sixthembodiment, the lens-barrels may be configured similarly to that of aneighth embodiment.

Eighth Embodiment

FIG. 9 is a diagram showing an eighth embodiment of the presentinvention and a total configuration of a scanning electron microscopeincluding an energy band-pass electron detector.

The scanning electron microscope shown in FIG. 9 is configured by ashape of eliminating the C2 lens from the seventh embodiment shown inFIG. 8. The scanning electron microscope of the eighth embodiment isfeatured in being easy to control since one stage of the condenser lensis configured.

However, an electron source of an electric field emitting type having asmaller light source diameter is typically used since a reduction rateof the primary electron beam 3 cannot be made high in comparison withthat of the seventh embodiment. The rest of the configuration is similarto that of the first embodiment, and the energy band-pass detection iscarried out similarly to the first embodiment. In this case, theconductive film A43 is arranged vertically to the optical axis of theprimary electron beam 3 at an interval between E×B20 for the detector Aand the aperture 24. Incidentally, similarly also in the scanningelectron microscopes from the second embodiment to the sixth embodiment,the lens-barrels may be configured similarly to that of the eighthembodiment.

Ninth Embodiment

FIG. 10 is a diagram showing a ninth embodiment of the present inventionand a configuration of a portion of a scanning electron microscopeincluding an energy band-pass electron detector.

In the scanning electron microscope shown in FIG. 10, an object lensthereof differs from that of the first embodiment. The object lens 44 ofthe ninth embodiment is configured by an in-lens type. According to thestyle, the sample can be placed in a lens field. Therefore, anobservation with a resolution higher than that of the object lens of thesemi-in-lens type can be carried out.

The energy band-pass detection is carried out similarly to the firstembodiment. Incidentally, similarly also in the scanning electronmicroscopes from the second embodiment to the eighth embodiment, theobject lens may be of the in-lens type.

Tenth Embodiment

FIG. 11 is a diagram showing a tenth embodiment of the present inventionand a configuration of a portion of a scanning electron microscopeincluding an energy band-pass electron detector.

In the scanning electron microscope shown in FIG. 11, an object lensthereof differs from that of the first embodiment. An object lens 45 ofthe tenth embodiment is of out-lens type. According to the style, thesample is exposed to a magnetic field of the object lens 45, andtherefore, an observation of a magnetic material sample or the like canbe carried out.

According to the tenth embodiment, unlike the previous embodiments, thesample is not placed in a magnetic field. Therefore, a number of signalelectrons having an energy width from 1 keV to the irradiation energy ofthe primary electron beam configuring the object of the band-passdetection linearly advance. Hence, according to the tenth embodiment, aband-pass detection system is provided on the sample side of the objectlens. The configuration of the tenth band-pass detection system is thesame as the configuration of FIG. 1-1.

However, the conductive film A43 is configured by an axisymmetriccircular disk shape provided with a hole of passing the primary electronbeam 3 at a center thereof, and arranged vertically to the opticalsystem of the primary electron beam 3 at an interval between the objectlens and the sample 50. The energy band-pass detection is carried outsimilarly to the first embodiment. However, according to the tenthembodiment, a structure does not exist at a route of a signal electronat an interval between the conductive film A43 and the sample.

Eleventh Embodiment

FIG. 12 is a diagram showing an eleventh embodiment of the presentinvention and a configuration of a portion of a scanning electronmicroscope provided with an energy band-pass electron detector.

In the scanning electron microscope shown in FIG. 12, a configuration ofan energy band-pass electron detector differs from that of the tenthembodiment. The configuration of the energy band-pass electron detectorof the tenth embodiment is configured such that the configuration of thefirst embodiment from E×B30 for the detector B to the acceleratingelectrode 28 is arranged at an interval between the object lens 45 andthe sample 50. The energy band-pass detection is carried out similarlyto that of the first embodiment.

Twelfth Embodiment

FIG. 13 is a diagram showing a twelfth embodiment of the presentinvention and a configuration of a portion of a scanning electronmicroscope provided with an energy band-pass electron detector.

In the scanning electron microscope shown in FIG. 13, a configuration ofan energy band-pass electron detector differs from that of the tenthembodiment. The configuration of the energy band-pass electron detectorof the tenth embodiment is configured such that a configuration of thefifth embodiment from E×B42 for the detector E to the acceleratingelectrode 28 is arranged at an interval between the object lens 45 andthe sample 50. The energy band-pass detection is carried out similarlyto that of the fifth embodiment.

Thirteenth Embodiment

FIG. 14 is a diagram showing a thirteenth embodiment of the presentinvention and a configuration of a portion of a scanning electrodemicroscope provided with an energy band-pass electron detector.

The scanning electron microscope shown in FIG. 14 differs from the tenthembodiment in an arrangement of an energy band-pass electron detector.In the thirteenth embodiment, the conductive film A43 and the detectorC27 are arranged at out of axis. An angle between the sample and theconductive film A43 falls in a range of 0° through 90°. The detector C27is arranged at a position at which a distance between the detector C27and the sample is larger than a distance between a face of theconductive film A43 to which the signal electron is impacted and thesample. According to the method, the conductive film A43 may not have acenter hole. The energy band-pass detection is carried out similarly tothat of the tenth embodiment.

Also respective configuring elements of the energy band-pass electrondetector which are provided at an interval from the object lens 45 tothe sample 50 according to the eleventh embodiment and the twelfthembodiment may be arranged at outside of axis similarly to thethirteenth embodiment. In that case, the conductive film A43 and theconductive film C39 may not have center holes. Also, the conductive filmA43 and the conductive film C39 may not be in parallel with each other.However, a distance between the sample 50 and the detector C27 needs tobe larger than a distance between the sample 50 and the conductive filmA43 and a distance between the sample 50 and the detector E41 needs tobe larger than a distance between the sample 50 and the conductive filmC39, respectively.

FIG. 15 shows a mechanism of making an energy for band-pass detectionvariable in a scanning electron microscope according to the presentinvention.

Plural conductive films having different thicknesses are arranged at aholder 47 attached with a linear guide. The holder 47 is arrangedvertically to the primary electron beam 3 and can be traversed by thelinear guide (not illustrated) to a state in which the primary electronbeam 3 passes through center holes of the respective conductive films46. The thicknesses of the respective conductive films differ from eachother, and therefore, a user can select the film thickness by an energyby which the band-pass detection is intended to carry out. A detectorthat detects the extremely low energy electron 6 to which the desiredenergy electron 4 is transformed is similar to that of FIG. 1-1. Any ofthe conductive film A43, the conductive film B31, and the conductivefilm C39 shown in the first through thirteenth embodiments may beprovided with the mechanism for making the energy variable shown here.

FIG. 16 shows an embodiment of a mechanism of making an energy forband-pass detection variable separately from that of the fourteenthembodiment in a scanning electron microscope according to the presentinvention.

The plural conductive films 46 having the different thicknesses arearranged at a holder 48 in a circular disk or fan shape. The holder 48is arranged vertically to the primary electron beam 3 and can be rotatedsuch that the center holes of the respective conductive films 46 arearranged in the state of passing primary electron beam 3 therethrough bya rotating mechanism (not illustrated).

A user can select the film thickness by the energy by which theband-pass detection is intended to carry out since the thicknesses ofthe conductive films differ from each other. A detector which detectsthe extremely low energy electron 6 to which the electron 4 of a desiredenergy is transformed is similar to that of FIG. 1-1. Any of theconductive film A43, the conductive film B31, and the conductive filmC39 shown in the first through the thirteenth embodiment may be providedwith the mechanism of making the energy variable shown here.

In all of the embodiments described above, there is a possibility ofdepositing contamination by impinging the electron beam in theconductive film A43, the conductive film B31, and the conductive filmC39. In order to restrain the deposition of contamination, therespective conductive films may be maintained at 200° C. or lower. Inall of the embodiments described above, means for preventing overheatingof the conductive film may be provided.

In the scanning electron microscope including plural detectors in theembodiment described above, there may be provided calculating means ofobtaining one signal from plural signals obtained from the separatedetectors. For example, in the fifth embodiment shown in FIG. 6, asignal obtained by the detector B27 is a signal which depends on anintensity of a desired energy. When a signal of the high energy electronobtained at the detector C41 is subtracted from the signal, there can besubtracted information of the high energy electron which has apossibility of being mixed to the detector B27 even by a small amount.

Although all of the embodiments described above relate to a scanningelectron microscope, the present invention is not limited to a scanningelectron microscope. For example, in a transmission electron microscope,when the detector of the present invention is arranged on a side of anelectron gun of a sample, energy band-pass detection with regard to anelectron which is generated on the side of the electron gun of thesample can be carried out simultaneously with observation of atransmitted electron image. In a scanning transmission electronmicroscope, when the detector of the present invention is arranged on aside of an electron gun of a sample, there can be obtained an energyband-pass image with regard to an electron which is generated on theside of the electron gun of the sample simultaneously with observationof a scanned transmitted electron image.

Fourteenth Embodiment

FIG. 17 is a diagram showing a fourteenth embodiment of the presentinvention and a configuration of a portion of a scanning electronmicroscope provided with an energy band-pass electron detector.

The scanning electron microscope shown in FIG. 17 is a low vacuumscanning electron microscope in which the inside of a sample chamber ismaintained typically at low vacuum of 10 through 1000 Pa. In the lowvacuum scanning electron microscope, the inside of the sample chamber ismaintained at 10 through 100 Pa by a vacuum discharge system (notillustrated). An upstream side of the electro-optical lens-barrel 13needs to be maintained in high vacuum more than 0.1 Pa in order toreduce influence of scattering the primary electron beam by a low vacuumatmosphere. A differential discharge orifice 200 is provided at aninterval between the electro-optical lens-barrel 13 and the samplechamber for that purpose.

In the scanning electron microscope shown in FIG. 17, the electrondetector portion differs from those of the embodiments of FIGS. 1-1through 14. The detector of the present embodiment includes an electricfield supplying electrode 202 for applying a positive voltage of 100through 500 V, a power source for electric field supplying electrode201, and a current amplifier 203 which is electrically connected to theconductive film 1. The electric supplying electrode 202 incorrespondence with a sensing surface of the detector is an electrode ina plate-like or mesh-like shape, and is arranged to the conductive film1 with an angle of 90° therebetween. Although the conductive film 1 ismaintained at a potential which is lower than that of the electricsupplying electrode 202, generally, the potential of the electricsupplying electrode is the ground potential.

The energy band-pass electron detector is realized by such aconfiguration even in the low vacuum scanning electron microscope.

According to the present embodiment, the desired energy electron 5 isdetected as follows under the low vacuum atmosphere.

The desired energy electron 5 generates the extremely low energy(several eV) electron 6 from a face of the conductive film 1 opposed tothe sample 50 similarly to the electron described in the above-describedembodiments. The extremely low energy electron 6 is accelerated in adirection of the electric field supplying electrode 202 by an electricfield supplied by the electric field supplying electrode 202. At thistime, the extremely low energy electron 6 is scattered along with a gasmolecule of the low vacuum atmosphere and ionizes the gas molecule witha constant probability. An ion 204 generated thereby moves toward theconductive film 1 a potential of which is lower than that of theelectric field supplying electrode 202. As a result thereof, adisplacement current flows in the current amplifier 203 connected to theconductive film 1 that is caused by the movement of the extremely lowenergy electron 6 and the movement of the ion 204. The displacementcurrent is in proportion to an amount of generating the extremely lowenergy electron 6, and therefore, an amount of generating the desiredenergy electron 5. A scanning electron microscope image with the desiredenergy electron 5 as a source of a signal is obtained by amplifying thedisplacement current by the current amplifier 203.

The angle between the conductive film 1 and the electric field supplyingelectrode 202 is not limited to 90°. Similarly to the embodiments shownin FIG. 1-2, FIG. 1-3, and FIG. 1-4, there may be a variation in thearrangement. Effects of the respective variations are similar to thosedescribed in the above-described embodiments.

Fifteenth Embodiment

FIG. 18 shows a fifteenth embodiment of the present invention and isanother mode of the embodiment of FIG. 17. The embodiment of FIG. 18 isa low vacuum scanning electron microscope similar to the embodiment ofFIG. 17 and has a mode excluding E×B30, and the detector B27 from thetenth embodiment shown in FIG. 11 and with the addition of a vacuumdischarge system which brings a sample chamber (not illustrated) underlow vacuum, the differential discharge orifice 200, the power source forelectric field supplying electrode 201, the electric field supplyingelectrode 202, and the current amplifier 203 electrically connected tothe conductive film 1.

The detection principle is similar to that of the embodiment of FIG. 17,and a detection three-dimensional angle can be enlarged by such aconfiguration.

Sixteenth Embodiment

FIG. 19 shows a sixteenth embodiment of the present invention andanother mode of the embodiment of FIG. 17. The embodiment of FIG. 19 isa low vacuum scanning electron microscope similar to the embodiment ofFIG. 17, and is configured by a mode excluding E×B30 and the detectorB27 from the thirteenth embodiment shown in FIG. 14, and with theaddition of a vacuum discharge system of bringing a sample chamber (notillustrated) under low vacuum, the differential discharge orifice 200,the power source for the electric field supplying electrode 201, theelectric field supplying electrode 202, and the current amplifier 203electrically connected to the conductive film 1.

The detection principle is similar to that of the embodiment of FIG. 17,and a space just above the sample can be given to another detector bysuch a configuration.

In the fourteenth to sixteenth embodiments of FIG. 17 through FIG. 19,the current amplifier 203 may be connected to the electric supplyingelectrode 202. In this case, although a polarity of the obtained signalcurrent is inverted to that of the case of connecting the currentamplifier 203 to the conductive film 1, a value thereof stayssubstantially the same. In this case, a floating mechanism is needed forthe current amplifier 203. In this case, there is achieved an advantagethat it is not necessary to reconnect the current amplifier 203 when thethickness of the conductive film is changed.

LIST OF REFERENCE SIGNS

1 . . . conductive film, 2 . . . electron detector, 3 . . . primaryelectron beam, 4 . . . low energy electron, 5 . . . desired energyelectron, 6 . . . extremely low energy (several eV) electron, 7 . . .high energy electron, 8 . . . mesh electrode, 9 . . . scintillator, 10 .. . light guide, 11 . . . photomultiplier, 12 . . . acceleratingelectrode, 13 . . . electro-optical lens-barrel, 14 . . . samplechamber, 15 . . . electron source, 16 . . . C1 lens, 17 . . . C2 lens,18 . . . two stages of scanning deflectors, 19 . . . detector A, 20 . .. E×B for detector A, 21 . . . semi-in lens type object lens, 23 . . .first convergent point of primary electron beam, 24 . . . aperture, 25 .. . second convergent point of primary electron beam, 26 . . . secondaryelectron, 27 . . . detector B, 28 . . . shielding electrode B, 29 . . .extremely low energy electron originated from low energy electron, 30 .. . E×B for detector B, 31 . . . conductive film B, 32 . . . desiredenergy high angle electron, 33 . . . extremely low energy electronoriginated from desired energy high angle electron, 34 . . . detector C,35 . . . E×B for detector C, 36 . . . low energy high angle electron, 37. . . extremely low energy electron originated from low energy highangle electron, 38 . . . detector D, 39 . . . conductive film C, 40 . .. extremely low energy electron originated from high energy electron, 41. . . detector E, 42 . . . E×B for detector E, 43 . . . conductive filmA, 44 . . . in-lens type object lens, 45 . . . out-lens type objectlens, 46 . . . plural conductive films of different thicknesses, 47 . .. holder of plural conductive films of different thicknesses, 48 . . .circular disk or fan-shaped holder of plural conductive films ofdifferent thickness, 49 . . . sample base, 50 . . . sample, 101 . . .trajectory of high energy electron after passing conductive film 1, 200. . . differential discharge orifice, 201 . . . power source forelectric field supplying electrode, 202 . . . electric field supplyingelectrode, 203 . . . current amplifier, 204 . . . ion

The invention claimed is:
 1. A charged particle radiation device,comprising: a charged particle source which generates a primary chargedparticle beam as a probe; a charged particle optical system; a samplestage having a sample provided thereon; a vacuum discharge system; anaperture which restricts a probe; a conductive film having a thickness;and a charged particle detector, wherein secondary charged particles aregenerated from the sample by irradiating the sample with the primarycharged particle beam, wherein secondary charged particles, transmittedfrom the conductive film opposite to the sample are detected by thecharged particle detector, wherein the conductive film is provided at aposition between the sample stage and the aperture, except within a pathof the primary charged particle beam, and wherein a distance between asensing surface of the charged particle detector and the sample stage isgreater than a distance between the sample stage and the conductivefilm, wherein the surface of the conductive film and the sensing surfaceof the detector are inclined with respect to each other, and wherein thethickness of the conductive film and the angle of inclination of thesurface of the conductive film relative to the sensing surface of thedetector allows for band-pass detection of only secondary chargedparticles having an energy within a predetermined range having a lowerlimit and an upper limit.
 2. The charged particle radiation deviceaccording to claim 1, wherein the conductive film is arrangedsubstantially perpendicular to an optical axis of the primary chargedparticle beam within +/−10 degrees, and an angle between the conductivefilm and the sensing surface of the detector falls in a range of 30 to150 degrees.
 3. The charged particle radiation device according to claim1, wherein the conductive film is arranged relative to the optical axisof the primary charged particle beam within an angle of 100 to 150degrees therebetween, and an angle between the conductive film and thesensing surface of the detector falls in a range of 30 to 150 degrees.4. The charged particle radiation device according to claim 1, wherein athickness of the conductive film falls in a range of 10 to 50000 nm. 5.A charged particle radiation device, wherein the charged particleradiation device according to claim 1 is a scanning electron microscope,further comprising means for supplying an electric field or a magneticfield guiding a tertiary charged particle generated from the face of theconductive film opposed to the sample in a direction of the chargedparticle detector at a space between the conductive film and the chargedparticle detector.
 6. The charged particle radiation device according toclaim 1, further comprising a holder attached to a linear guide, whereinthe holder holds a plurality of conductive films each having a differentthicknesses, wherein each of the plurality of conductive films has acenter hole allowing the probe to pass through when a respectiveconductive film of the plurality of conductive films is used.
 7. Amethod of detecting charged particles of a charged particle radiationdevice, comprising: irradiating a sample with a primary charged particlebeam; and detecting, by a charged particle detector, secondary chargedparticles transmitted from a conductive film having a thickness whichare generated from the sample by irradiating the sample with the primarycharged particle beam, wherein the conductive film is provided at aposition between the sample stage and the aperture, except within a pathof the primary charged particle beam, and wherein a distance between asensing surface of the charged particle detector and the sample stage isgreater than a distance between the sample stage and the conductivefilm, wherein the surface of the conductive film and the sensing surfaceof the detector are inclined with respect to each other, and wherein thethickness of the conductive film and the angle of inclination of thesurface of the conductive film relative to the sensing surface of thedetector allows for band-pass detection of only secondary chargedparticles having an energy within a predetermined range having a lowerlimit and an upper limit.
 8. The method of detecting charged particlesaccording to claim 7, wherein the conductive film is arrangedsubstantially perpendicular to an optical axis of the primary chargedparticle beam within +/−10 degrees, and an angle between the conductivefilm and the sensing surface of the detector falls in a range of 30 to150 degrees.
 9. The method of detecting charged particles according toclaim 7, wherein the conductive film is arranged relative to the opticalaxis of a primary charged particle beam within an angle of 100 to 150degrees therebetween, and an angle between the conductive film and thesensing surface of the detector falls in a range of 30 to 150 degrees.10. The method of detecting charged particles according to claim 7,wherein a thickness of the conductive film falls in a range of 10 to50000 nm.
 11. The charged particle radiation device according to claim7, further comprising a holder attached to a linear guide, wherein theholder holds a plurality of conductive films each having a differentthicknesses, wherein each of the plurality of conductive films has acenter hole allowing the probe to pass through when a respectiveconductive film of the plurality of conductive films is used.